A coupler is a device used to secure a work attachment to a work vehicle. They generally have jaws that receive pins on the work attachment.
At least one of the jaws is moved by an actuator. This allows the jaws to engage and release the pins thereby securing and releasing the work attachment to the coupler as required.
The actuator applies a driving or engagement force to the moveable jaw to retain the pin therein. Generally another jaw of the coupler faces in the opposite direction to the moveable jaw. Therefore the driving/engagement force of the actuator also forces another pin on the work attachment into another jaw of the coupler.
However, if the actuator fails then the moveable jaw can move and release the pin. This is referred to as lack of engagement force and provides a significant health and safety risk. There have been a number of recent high profile accidents involving failures such as this causing injury to people.
Lack of engagement force is caused by failure of an actuator. This can be for several reasons including loss of hydraulic pressure through leaks or other damage.
Therefore, it is known to have locking systems to secure a moveable jaw. These protect against failure of actuators by securing the moveable jaw with respect to the coupler to retain the pin in the jaw.
One example of these devices is that disclosed in PCT Application No. GB/2007/003324 to Miller UK Limited.
This coupler has a main body to support a pivotal locking member. The locking member prevents a pivoting jaw from moving should the actuator fail. This is achieved by gravity biasing the locking member downwards so that it abuts the jaw thereby holding this and preventing release of the pin.
The locking mechanism of the Miller coupler can be released by moving the coupler through a number of steps. These steps involve inverting the coupler so that gravity causes the member to pivot away from the jaw. This allows the jaw to be retracted by the actuator.
However, it is an inherent problem of this type of coupler that this must be inverted to enable the jaw to release the pin. This means that it can be a time consuming and awkward process to release the work attachment from the coupler.
In addition, relying on gravity to move the locking member means that the system is not fail safe. For instance, dirt or debris may hinder movement of the locking member and prevent securing and/or releasing the jaw.
Yet a further failing of the available couplers is that they are generally configured to work attachments having a predetermined pin separation. Therefore the couplers are not able to be used with different work attachments where the pin spacing varies. This can be a significant limitation on the available couplers.
An additional limitation to the effectiveness of similar devices is that they are designed specifically for use with a fixed coupler. Many modern couplers now incorporate a tilting section which permits the attachment to be angled up to 90 degrees in each direction. Any angle less than perpendicular will reduce the effectiveness of a gravity operated locking member. Therefore, it would be advantageous to have a locking mechanism to secure a jaw with respect to a coupler to ensure that a pin is retained therein.
In addition, it would be advantageous to have a coupler which addresses the issues with the prior art.
Alternatively it is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.